According to the press release - 'Iray is an example of a progressive renderer that helps delivers results in seconds, not minutes.' As you know mental ray is currently integrated in Autodesk® 3ds Max®. I hope that when the next version of 3ds Max comes out it will have mental ray 3.8, which includes iray now. I found this in the PDF you can download from the mental images site (see below for link) "...iray will be available to mental images’s OEM partners and we expect that they will make it available it in their applications in accordance with their own release plans..." I would love to be able to use this in my architectural viz work. The PDF goes on to say "...The exact GPU hardware specifications vary with content and application requirements and CUDA-enabled GPUs will be required for high performance. While all CUDA-enabled GPUs are supported, iray’s memory requirements will make NVIDIA Quadro®, QuadroPlex® and Tesla® systems for workstations as well as Tesla server units the platforms of choice in most situations..." So if you want the kind of performance seen in the demo video of iray in action which hosted by Michael Kaplan, VP of Strategic Dev elopement over at mental images I guess you'll have to have deep pockets

From the web site
".... mental ray 3.8 includes iray®, the world’s first interactive and physically correct, photo realistic rendering solution. With iray, users can quickly create life-like images of their creations by using intuitive, real world approaches and interactively exploring their results through the processing power of NVIDIA® graphics processing units (GPUs). iray accelerates the creative process by accurately simulating the physical world, enabling designers, engineers and consumers to use materials, lighting and settings that truly resemble what they experience every day. iray makes this process interactive by progressively refining the image until the desired detail is achieved, becoming increasingly faster as more GPUs are employed, enabling the play of light, shadow and reflection to be studied. With iray, interactive realism is now a reality.

iray works with standard multi-core CPUs, however CUDA enabled GPU hardware will significantly accelerate the final image generation and provide interactive convergence of complex global illumination effects. Customers of mental ray 3.8, or applications that integrate mental ray 3.8, will have the option of exposing iray..."

For some pictures and for the short video mentioned above, you can go to Autodesk's AREA web site or get info straight from the mental images web site Here you can also download that information PDF. In it I found what I consider a good short answer of what iray is: "...iray is a GPU accelerated photo realistic rendering technology offered as a rendering mode of mental ray 3.8..." It is not a real time raytracer and does not replace the mental ray renderer. Those of us who still use MR in 3ds Max will still want render as usual to do things like fine tune our renderings with all the options available in MR.

One thing I found a little disappointing in the news about this is "...When running on a system that lacks compatible NVIDIA GPU resources, iray will operate as a CPU-based renderer, albeit significantly slow er..." I just wish I knew how 'significantly slower' it will be. Oh well, this is definitely welcomed technology.